To evaluate the role of serum cytokines in the pathogenesis of respiratory syncytial virus (RSV) infection in infants with low birth weight (LBW).
Sheng et al BMC Pediatrics (2017) 17:205 DOI 10.1186/s12887-017-0961-2 RESEARCH ARTICLE Open Access Low birth weight contributed to increased serum IL-6 levels in infantile respiratory syncytial virus infection Yuan-Jian Sheng1, Shan-Shan Xu2, Xue-Jing Li1, Jin-Ling Liu1, Xi-Ling Wu1 and Xue-Feng Xu1* Abstract Background: To evaluate the role of serum cytokines in the pathogenesis of respiratory syncytial virus (RSV) infection in infants with low birth weight (LBW) Methods: A prospective observational study was performed, and hospitalized children with lower respiratory tract infection (LRTI) were recruited Three hundred fifty-eight patients < year met the inclusion criteria: 116 patients had only RSV infection (RSV group); 242 patients had no RSV or other specific pathogen (non-RSV group) Serum interleukin-2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ) were detected through flow cytometry Results: No significant differences in serum IL-2, 4, 6, 10, and IFN-γ levels were observed between the RSV and non-RSV groups For RSV infected infants with or without wheezing, delivery mode had no obvious effect on the changes of serum cytokine levels However, the level of IL-6 in the RSV-infected infants with LBW was significantly higher than that in infants with normal birth weight Conclusions: Serum IL-6 level was significantly increased in RSV infected infants with LBW It is likely that the specific serum cytokine pattern will contribute to our understanding of the pathogenesis of RSV infections, especially in RSV-infected infants with LBW Keywords: Cytokine, Infant, Lower respiratory tract infection, Low birth weight, Respiratory syncytial virus Background Lower respiratory tract infection (LRTI) is the leading cause of global child mortality Respiratory syncytial virus (RSV) is believed to be the most important viral pathogen causing LRTI in young children Furthermore, the incidence for severe LRTI was highest in infants aged 0–11 months [1] RSV is not only the leading pathogen of LRTI including pneumonia and bronchiolitis, but is also closely associated with the development of asthma [2] A number of clinical epidemiology studies have revealed that there is a strong association between RSV bronchiolitis in infancy and the development of wheezing or asthma in later childhood About 40% of children after severe RSV bronchiolitis subsequently * Correspondence: xuxuefeng@zju.edu.cn Department of Respiratory Medicine, The Children’s Hospital, Zhejiang University School of Medicine, Hangzhou 310052, China Full list of author information is available at the end of the article develop asthma [2, 3] Despite the importance of RSV as a respiratory pathogen, the underlying mechanisms of the development of subsequent wheezing and asthma following primary RSV infection remain unclear RSV infection may increase the susceptibility to developing allergic immune responses by breaking immune tolerance to allergens early in life through regulatory T cells [4] Moreover, RSV-induced neurogenic inflammation appears to potentiate neural pathways that favor bronchoconstriction and mucus production [5] Interestingly, studies have shown that infection with RSV also results in a significant increase in proinflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α, contributing to development of recurrent wheezing or asthma [3] Our previous study has shown that low birth weight (LBW) or intrauterine growth retardation significantly increases the risk of childhood asthma Children with © The Author(s) 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated Sheng et al BMC Pediatrics (2017) 17:205 LBW have an approximately 16% higher risk of asthma compared with those with normal birth weight (NBW) [6] Another study by Rossi et al further revealed that LBW was not only associated with the increased risk of asthma or wheezing, but also with RSV infection severity [7] Although we recognize the significant role of low birth weight in infantile RSV-induced LRTI or wheezing, the mechanism of this phenomenon remains unknown In view of the potential role of cytokines, we hypothesized that LBW induces a specific cytokine profile in infantile bronchiolitis or wheezing induced by RSV infection, leading to more significant manifestations related to asthma The present study aims to evaluate the possible role of cytokines in the pathogenesis of RSV infection in infants with LBW Methods Data collection In this prospective observational study, hospitalized children with lower respiratory tract infections (LRTI) from the Respiratory Department of the Children’s Hospital of Zhejiang University School of Medicine between January 2013 and December 2014 were recruited LRTI, including bronchiolitis and pneumonia, has been defined as equivalent to clinical pneumonia, which is characterized by acute onset cough or difficulty breathing with fast breathing for age [8] Inclusion criteria were hospital admission, LRTI, age